Why toilet flange resting on top of finished floor

Hello:
I have read many inputs advising that a toilet flange should rest on top of the finished floor (if at all possible). Can someone advise why this is?
Is it to ensure a certain amount (height) of the flange is inside the base of the toilet so that ideally only one wax ring is required?

Thanks
Raymes

It puts the flood plane on top of the floor rather than embedded in it, and provides a shorter bolt length that makes it more stable, and keeps the wax thickness at a more ideal thickness.

Or, put another way, that's the way toilets are designed.

As it stands the wax ring is the weakest joint in the waste system. Anything less than right increases chances of leakage! Leakage can ruin wood!

Need I say more?

flange

To answer your question, YES. Toilets have varying spaces under them where they attach to the flange. By putting the flange on top of the floor you are assured that even those with a maximum space will still seal with the standard wax ring. IF the flange were not on top of the floor and the conventional wax ring is used, there is a possibility that it would not even come in contact with some toilet's base and thus give no seal at all.